C-Parameter and Jet Broadening at PETRA Energies

TL;DR

This paper measures the C-parameter and jet broadening variables in e+e- annihilation at PETRA energies, compares results with QCD calculations, and determines the strong coupling constant _s at various energies.

Contribution

First measurement of the C-parameter at PETRA energies and application of extended resummed calculations to jet broadening variables, improving _s determination.

Findings

_s(35 GeV) = 0.1448 +0.0117 -0.0070

_s(44 GeV) = 0.1392 +0.0105 -0.0074

_s(M_Z) = 0.1177 +0.0035 -0.0034

Abstract

e^+e^- annihilation data recorded by the JADE detector at PETRA were used to measure the C-parameter for the first time at \sqrt{s}= 35 and 44 GeV. The distributions were compared to a resummed QCD calculation. In addition, we applied extended resummed calculations to the total and wide jet broadening variables, B_T and B_W. We combined the results on \alpha_s with those of our previous study of differential 2-jet rate, thrust, and heavy jet mass, obtaining \alpha_s(35 GeV) = 0.1448 +0.0117 -0.0070 and \alpha_s(44 GeV) = 0.1392 +0.0105 -0.0074. Moreover power corrections to the mean values of the observables mentioned above were investigated considering the Milan factor and the improved prediction for the jet broadening observables. Our study, which considered e^+e^- data of five event shape observables between \sqrt{s}= 14 and 183 GeV, yielded \alpha_s(M_{Z^0})=0.1177 +0.0035 -0.0034.